| This study researched the soil organic carbon loss, factors and the organic carbon distribution in the young growth of the promote update forest, the Cunninghamia Lanceolata plantation and the Castanopsis Lanceolata plantation (from April to September,2012) by using the method of runoff plots. The three young forests were regenerated from the cutting-blanks of evergreen broad-leaf forests. The objective was to reveal the differences of soil organic carbon loss under different regeneration ways in mid-subtropical mountainous area of Southern China, to provide theoretical basis for the way to maintain and to promote the forest soil organic carbon content. The results were as follows:(1) In the promote update young forest, the totle soil carbon loss, the amount of dissolved organic carbon and the carbon loss in sediments were respectively15.21kg·ha-1ã€2.76kg·ha-1and12.45kg·ha-1. The totle soil carbon loss, the amount of dissolved organic carbon and the totle soil carbon loss in sediments of the Cunninghamia Lanceolata young plantation were respectively7.04times3.21times and7.89times as much as that in the promote update young forest. And they in the Castanopsis Lanceolata young plantation were respectively7.61times,3.72times and8.47times as much as that in the promote update young forest. So the three loss in the young plantations were significantly (P<0.05) or extremely significantly(P<0.01) higher than that of the promote update young forest. It showed that artificial afforestation could lead to more serious organic carbon loss in forest lands, compared with the promote update mode.(2)The distribution trend of the totle soil carbon loss was consistent in the three forest lands, and the percentage of organic carbon in sediments accounted for the largest(the mean value above60%); The carbon content in sediments was mainly between3%and5%, but that in the promote update young forest had significant difference (P<0.05) with that in the Cunninghamia Lanceolata young plantation and the Castanopsis Lanceolata young plantation. The dissolved organic carbon content of runoff in three young forest lands was not significantly different, and the average dissolved organic carbon content of three young forest lands was all around9.50mg·l-1. (3) In the promote update young forest, the totle soil carbon loss had extremely significant positive correlation (P<0.01) with rainfall and runoff, but in the two young plantations, the extremely significant positive correlation (P<0.01) was only found between the totle soil carbon loss and the sediment amount. There was extremely significant positive correlation (P<0.01) between dissolved organic carbon erosion and the runoff in three young forests; At the same time, the extremely significant positive correlation (P<0.01) was found between the total organic carbon loss of sediments and sediments in the promote update young forest, but in two young plantations that was found between the total organic carbon loss in sediments and runoff. It made clear that in the early stage of forest regeneration, water and soil loss is the main reason to result in the loss of soil carbon, and under different modes the main influence factors of carbon loss were different.(4) The study of distribution of carbon in sediments found that:The percentage of LFOC in sediments and the particle size distribution of sediments in the two young plantations were almost the same, and the average ratio of LFOC in the sediment was around17%. In the particle size distribution, the content of1.00-0.25mm fraction was highest,2.00-1.00mm second,<0.02mm least; In addition, the contribution of1.00-0.25mm fraction to carbon loss was largest. |
